BOULDER—As the U.S. Senate considers climate change legislation, 18 leading scientific organizations have sent a letter to members of the senate reaffirming the scientific consensus that climate change is occurring and that greenhouse gases from human activities are the primary driver.

Richard Anthes, president of the University Corporation for Atmospheric Research, added his signature to the letter on behalf of UCAR, a nonprofit organization governed by 75 member universities granting Ph.D.s in atmospheric and related Earth system sciences.

Sent to all senators on October 21, the letterstates in part:

"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science. Moreover, there is strong evidence that ongoing climate change will have broad impacts on society, including the global economy and on the environment."

In the United States, these impacts could include sea level rise for coastal states, greater chances of extreme weather, regional water shortages and floods, and wildfires, the letter said. The organizations noted that a dramatic reduction in greenhouse gas emissions will be necessary to avoid such serious impacts and warned that adaptation will be required to address impacts that are already unavoidable. Adaptation methods include improved infrastructure design, sustainable water management initiatives, modified agricultural practices, and improved responses to incidents of hazardous weather.

In June 2009, the U.S. House of Representatives passed its version of a climate change bill. The U.S. Senate Environment and Public Works Committee, the first of several Senate committees to do so, is expected to begin consideration of climate change legislation later this month.

American Association for the Advancement of Science American Chemical Society American Geophysical Union American Institute of Biological Sciences American Meteorological Society American Society of Agronomy American Society of Plant Biologists American Statistical Association Association of Ecosystem Research Centers Botanical Society of America Crop Science Society of America Ecological Society of America Natural Science Collections Alliance Organization of Biological Field Stations Society for Industrial and Applied Mathematics Society of Systematic Biologists Soil Science Society of America University Corporation for Atmospheric Research

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